1. Field of Invention
The present invention relates to a method of manufacturing a dynamic random access memory (DRAM). More particularly, the present invention relates to a method of manufacturing trench type DRAM capacitor.
2. Description of Related Art
Trench DRAM capacitor is a widely used type of capacitor in association with other semiconductor devices. As soon as a trench is formed in an insulation layer above a substrate, polysilicon material is deposited into the trench to form a polysilicon layer that serves as the lower electrode of the capacitor. To prevent possible connection with a neighboring capacitor, chemical-mechanical polishing operation is conducted to remove the polysilicon material outside the trench area. In general, a layer of insulation material having a thickness of about 1500 .ANG. to 2000 .ANG. is removed in the polishing operation so that the independence of circuit between neighboring capacitors is ensured. In practice a thickness as high as 4000 .ANG. may be removed, and hence the degree of planarity for the entire substrate structure may be affected. While several chemical-mechanical steps are performed in DRAM fabrication, global thickness differences may be cause, and this has impact on high aspect ratio etching. furthermore, it is difficult to control the capacitor at a pre-defined height level, and so there is much variation in the capacitance of each capacitor.